Biomedical Engineering Reference
In-Depth Information
4 Biological Agents, Effects,
Treatment, and Differential Diagnosis
ZYGMUNT F. DEMBEK AND THEODORE J. CIESLAK
finding in an ill, febrile patient is highly suggestive
of a diagnosis of anthrax. Definitive diagnosis may
be made by isolating
B. anthracis
from a culture
of blood (or spinal fluid, as 50% of inhalational
anthrax victims will develop hemorrhagic menin-
gitis) [5].
4.1 Disease: Anthrax
4.1.1 Causative Agent
Bacillus anthracis
is a sporulating Gram-positive
rod. Three forms of anthrax are known: inhala-
tional anthrax from inhalation of aerosolized
anthrax spores, gastrointestinal anthrax from eating
food contaminated with the bacterium, and cuta-
neous anthrax from skin contact with an item
contaminated with anthrax spores [5].
4.1.4 Differential Diagnosis
The differential diagnosis for inhalational anthrax
must include coccidiomycosis, diphtheria, menin-
gitis, pneumonia, aerosol exposure to staphylo-
coccal enterotoxin B (SEB), pneumonic plague or
tularemia, invasive group A streptococcal pneu-
monia, and other forms of severe acute pneu-
monitis. With SEB, no prodrome would be evident
prior to onset of severe respiratory symptoms.
Patients with plague, tularemia, or invasive group
A streptococcal pneumonia are far more likely
than those with anthrax to have pulmonary infil-
trates [5].
4.1.2 Clinical Description
The incubation period for inhalational anthrax is
1-6 days. Patients with inhalational anthrax typi-
cally have a biphasic illness with a nondescript
initial phase followed by an acute second phase.
Initially, non-specific symptoms appear, similar
to a common upper respiratory infection: fever,
fatigue, malaise, myalgia, mild chest pain, and
a non-productive cough. These initial symptoms
are often followed by a brief period of improve-
ment (from hours to 2-3 days) followed by a
rapid onset of severe respiratory distress with
dyspnea, diaphoresis, stridor, and cyanosis. Chest
wall edema may be observed. Without treatment,
shock and death follow within 24-36 hours of onset
of severe symptoms [5].
4.1.5 Medical Management
Inhalational anthrax is almost always fatal if treat-
ment is begun after the patient is symptomatic.
Penicillin has been the treatment of choice for
naturally occurring strains. Resistant strains do
occur; in the absence of sensitivity data, empiric
treatment should be instituted with ciprofloxacin
400mg IV q12h (10-15mg/kg IV q12h in children)
or doxycycline 100mg IV q12h (2.2mg/kg IV
q12h in children). When clinically appropriate, oral
antimicrobials can be given: ciprofloxacin 500mg
po BID (10-15mg/kg po q12h) or doxycycline
100mg po BID (2.2mg/kg po q12h) (adult dose).
4.1.3 Diagnosis
Because of the urgent need to begin therapy,
an initial diagnosis of anthrax should be made
clinically. A widened mediastinum is the hall-
mark clinical association in inhalational anthrax.
In the absence of an alternative explanation, such a
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